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Full text of "The Morphology And Evolution Of The Apes And Man"

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Air-Sacs,In all Anthropoids, except the Gil/i.-cns of the genus Hyhbatef, there are air-sacs coLEEsrmicating
with the ventricles of the larvnx.    Thev varv in size in
different examples of each Ape, and Yrclik ,411 points out that thej* vary with age and sex. In the Chimpanzee it lies immediately under the platysma, and its smooth, shining walls are formed by the deep cervical fa>cia. It consists of a central and two lateral parts. The former extends upwards to the excavated hyoid bone, and downwards to the lower border of the manubrium sterci between the origins of the sterno-mastoic muscles. The orifices of the latter lie under the eleido-niastoid inuseles, and a finger passed into them can explore the entire axillae. Manv muscles, vessels and nerves form ridges
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in the walls of the sac. The central part communicates with the laryngeal ventricles through the thyro-hyoid membrane. The Gorilla has a complicated group of air-sacs branching off from a central cavity composed of conjoined saccules. There is a median, unpaired, infra-hyoid saccule passing upwards; two saccules pass upwards and outwards to the submaxillary region; and two large ones run downwards and outwards as axillary saccules. From the latter two small diverticula form pectoral saccules. Occasionally the central conjoined saccules have lateral diverticula. The conditions of the air-sacs are very complex in the Orang, and many descriptions have been published by Pick $47), Milne-Edwards (268), Camper (237), Duvernoy (53) and others. Deniker and Boulart show, from an examination of several animals, that there are two air-sacs in the Orang, which increase in size with age; and they are more frequently unequal in size in the male than